FIG. 1 shows a circuit switched mobile telecommunication system 100 according to the prior art. The system 100 comprises a CN 104 that comprises at least one Mobile Switching Center (MSC) and a RAN 102. The RAN 102 comprises at least one controlling unit 106 that is connected to the MSC. The controlling unit 106 is a Base Station Controller (BSC) in a GSM system and a Radio Network Controller (RNC) in a UMTS system. Each controlling unit is further connected to at least one Base Station (BS) and each BS is respectively adapted to communicate over a radio interface 108 with at least one Mobile Terminal (MT). The MSC is also connected to a Public Switched Telephone Network (PSTN) via a Gateway MSC (not shown in the figure). In a circuit switched system as shown in FIG. 1, voice and data sessions are guaranteed network resources via signalling, i.e. the Mobile Terminal (MT) signals its network resource demands to the system. If resources are available, a dedicated communication circuit that guarantees resources for the session is set up through the network.
A current networking trend is to provide “IP (Internet Protocol) all the way” to wireline and wireless units. The objectives are to simplify infrastructure, to support a wide range of applications, and to support heterogeneous user demands on the communication service. This trend is applicable to wireless systems such as GSM (Global System for Mobile communication), GPRS (General Packet Radio Service), and UMTS (Universal Mobile Telecommunication System).
One step towards an all IP wireless system is to replace the traditional circuit switched technology by packet switched IP technology. By doing so, some of the network resource management mechanisms that are built into the system are no longer available and need to be replaced. The architectural components such as the MSC, Controller and the BS are still present but IP routers have replaced circuit switched network elements in order to provide IP based transmission. I.e., IP routers are introduced in network, e.g. within the CN and between the CN and the RAN and between and BS and a BSC in the RAN. In the wireless parts, the packet transfer over the radio interface (between a BS and a MT) is controlled by other protocols such as RLC, MAC and RRC that e.g. manage radio resources and provide reliable links.
In such a system, traffic circuits can be emulated by setting up IP tunnels between the logical components. The IP tunnels must provide a bearer service equivalent to that provided by the circuits in a circuit switched system.
The big challenge in this convergence lies in supporting multiple services with different Quality of Service (QoS) requirements that is providing e.g. an appropriate delay, jitter and packet loss guarantees for each service. To provide appropriate QoS, different types of resources (e.g. radio resources, network resources and power resources) have to be managed in the systems. Architectural components managing resources, e.g. in the Radio Access Network (RAN) and the Core Network (CN), of these systems are defined in different standards.
As stated in the previous section the trend is that future telecommunication systems will be all IP multi-service systems. FIG. 2, shows an example of a packet switched wireless system 200, e.g. a third generation (3G) UMTS system. The system comprises a CN with IP based transmission that comprises IP routers R and support nodes; a Serving GPRS Support Node (SGSN) that e.g. implements mobility functions and Gateway GPRS Support Node (GGSN) that implements interoperability with other systems, e.g. the Internet or PSTN. The system further comprises RANs that comprise a controlling unit 204, Base Stations BS and IP routers R. In the system 200, the SGSN, the GGSN, the controlling unit 204 e.g. an RNC and the BS (and other network elements) are interconnected by means of the IP routers R. This system is thus optimised for delivering IP packet switched services and its system architecture differs from the circuit switched architecture. Both the RAN and the CN are IP networks where logical functions (e.g. Radio Resource Management (RRM)) are distributed, e.g. in the RNC and in the SGSN.
The 3G wireless system needs to support multiple services (e.g. voice conversations, data transfers, streaming media, etc.) which have different transport QoS requirements. Sessions will often span over the RAN and the CN of the system and into other peering telecommunication systems (e.g. a PSTN).
Moreover, services in 3G systems usually utilize so called bearer services that have different QoS characteristics for transporting the service through the system. UMTS, defines e.g. four QoS classes (conversational, streaming, interactive, background) for the UMTS bearer service. A bearer service can also be layered and partitioned between system domains. FIG. 3 shows the UMTS Bearer Service as an example. It is based on two components, the Radio Access Bearer (RAB) service and the CN bearer service. The UMTS Bearer Service ranges between the MT to the CN, and the (RAB) service from the MT to the CN (and the other way around) and the CN bearer service ranges within the CN.
It should be noted that the bearer services make use of IP based networks to provide the transport. To provide the appropriate bearer service, network resources within the IP network have to differentiate between traffic flows, and have to be managed so that resources are available when needed. These requirements have to be met in all parts of the system to provide appropriate end-to-end QoS. There is a need of QoS management functions in the different system domains to implement the bearer service in each system domain. A UMTS system relies on a number of bearer service managers, e.g. a RAB service manager and a CN service manager, that establish, modify and maintain their respective bearer service. The bearer service managers are located in different nodes (e.g. RNC, SGSN, GGSN) depending on in which system domain they manage the bearer service. The radio resources are thus managed by one or more bearer service managers (e.g. a RAB service manager) that handles the radio resources, i.e. the radio resource manager may be a part of the RAB service manager.
In the sections above a UMTS system is used as reference for describing the need of network resource management functions in IP-based wireless systems. The description is, however, equally applicable for wireless systems based on other current and evolving standards e.g. cdma2000, GSM/GPRS as well as evolving releases of the UMTS standard. Other systems and releases may be partitioned into other system domains, use other terminology for describing the transport service and characterise the transport in other ways, but they will still use IP networks for transport of different services. This implies that the systems need network resource management functions for being able to provide transport services with certain QoS characteristics.
As described above, the present invention relates to systems using IP based transmission. There are some characteristics that are common for IP-based systems that relate to the nature of how IP networks work and how they are designed. These characteristics are discussed in the following.
The IP protocol is designed to be used in networks where different traffic flows share network resources equally. This means that the received QoS depends on the current load in the network. To provide QoS guarantees for specific traffic, QoS mechanisms are required. Mechanisms and methods applied for this purpose are described below.
Traffic in these systems will usually be forwarded according to routes set up by distributed and dynamic intra- and inter-domain routing protocols such as OSPF (Open shortest Path First) and BGP (Border Gateway Protocol). These routing protocols automatically detect network failures and set up new routes to avoid the failure.
The network topologies in IP-based systems are less hierarchical than those in circuit switched systems. In 3G systems that are optimised for IP services the topology will be distributed, as can be understood from FIG. 2.
The packet switched nature of IP-based networks makes them very well suited for traffic aggregation. This will be used especially in RANs where link deployment can be very expensive. Redundant links will be used where network reliability is critical or to add resources between hot spot sites. Redundant links 206 can be seen in FIG. 2.
There are typically two known ways to provide QoS guarantees for bearer services in the RAN and the CN that use IP networks for transport; either to use QoS mechanisms such as Differentiated Service (DiffServ) or to over-dimension the network.
The (DiffServ) architecture is one QoS framework that can be applied to provide mechanisms for setting up traffic classes in the network to enable differentiation of network resources among services. At system set up, the different traffic classes are dimensioned to ensure that each class has sufficient resources. Dimensioning is based on service characteristics and assumed usage statistics.
For systems that provide one or a few services, over-dimensioning of the network is usually used to ensure sufficient resources. Service monitoring often complements over-dimensioning to discover where network resources are lacking and to trigger re-dimensioning of the network. For both the Diffserv capable and the “single service” network case described, dimensioning and re-dimensioning are done manually and there is no real-time control of the actual resource usage.
A solution based on dimensioning will work as long as the dimensioning assumptions hold. However, if the assumptions break, e.g. if the usage behaviour changes or a network link fails, some network links can get over-utilised causing degraded quality for some active sessions. FIG. 4 depicts a RAN comprising an RNC connected via IP routers to a number of BS and a number of MT. FIG. 4A shows a normal operation while FIG. 4B shows a scenario during a link failure 402 that results in insufficient resources on another link 404. It is possible to prevent this situation by over-dimensioning resources so that minor dimensioning mistakes can be handled. This will, on the other hand, cause the network to be under-utilised most of the time. The problem with the dimensioning method is that it is impossible to foresee all future events at the time of dimensioning and still achieve reasonable network utilisation. There is a need for a mechanism that keep track of how resources are used on each link in the network and that can reject setup of new bearer services over links where there are no resources left to fulfil QoS requirements. The same reasoning holds for the Diffserv case where network resources are provisioned to different service classes based on assumption on traffic loads and characteristics. There is a need for a mechanism that manages and controls the resources in each traffic class.
The problems described above can be extended to the scenario when a Mobile Terminal (MT) in a wireless system moves and causes handover between base stations. As the terminal moves, the need for resources in different parts of the network changes. It is impossible to predict how the terminal will move and thereby where network resources will be needed. If there is no entity in the system that controls and sets up resources, network links can get over-utilised at handover.
FIG. 5 shows a RAN comprising a RNC connected to a number of BS via IP routers R and MT. “ok” means that a connection has sufficient resources and “nok” means that a connection has insufficient resource. “1” means a first scenario and “2” means a subsequent second scenario. FIG. 5 illustrates another problem that occurs when sessions are denied to start even if resources are available in the system. Consider a situation when a terminal tries to start a session. The session can be denied due to lack of network resources as in FIG. 5a, lack of radio resources as in FIG. 5b, or lack of both radio and network resources as in FIG. 5c. In some cases it would be possible to accept the session if the terminal changed its point of connection from the currently serving base station to another one.
These problems, implies that there is a need for a resource management mechanism that have full knowledge of resource usage/allocation and network topology in the IP network.
An additional requirement on the bearer service delivered by a wireless system is that end-to-end QoS can be provided through all parts of the network. It is hard, if not impossible, to dimension all network parts in a system to meet all possible QoS requirements while not causing the network to be under-utilised most of the time. The difficulty to provide end-to-end QoS by dimensioning grows as the network and system grows.
In EP 1 059 792, a radio resource management for the radio link in a wireless IP system is showed and it describes a method and system that maps IP QoS parameters or requests to radio resource requests. It also addresses procedures for applying the mapping and managing the radio resources.
EP 1 059 792 does not address resource management issues for an IP network of a wireless system.
Thus, an object of the present invention is to achieve automatic network resource management for providing appropriate end-to-end QoS for sensitive services throughout a wireless and IP transmission based communication network.
Another object of the present invention is to enable efficient monitoring of how network resources are used by bearer services/calls on a per link basis and over time without the need to make measurements in routers.